After cleaning the debris and reframing the roof, lay down a base (sheathing). Eight-foot, 1/2-inch-thick plywood is standard sheathing material. Measure the opening of the section of roof to be shingled, cut the plywood to size and nail to roof rafters. Stagger the sheathing in a brick pattern for extra strength. Do not place an entire 8-foot section of plywood onto roof. Such a long piece is structurally unstable in the middle. Continue to install in brick pattern, staggering the plywood seams until the open area is covered.